Isolation and identification of a pathogen, Providencia rettgeri, in Bombyx mori

A Gram-negative, rod-shaped bacterium, SY-1 strain, was isolated from a naturally infected silkworm Bombyx mori that was suffering from the common infection septicemia. The colony was round, slightly convex, smooth, moist, translucent, regular-edged and milky white on nutrient agar medium. The SY-1 was identified as a putative strain of Providencia rettgeri through its physiological and biochemical properties, and phylogenetic analyses performed using the 16S rRNA gene sequence. The SY-1 was identified as a putative strain of P. rettgeri. This is the first report demonstrating that P. rettgeri is pathogenic to B. mori. The identification of this strain adds to known kinds of pathogens that cause bacterial septicemia in the silkworm. This study aids the understanding of the prevention and control of the bacterial septicemia pathogens of B. mori.   Key words: Bombyx mori, bacterial septicemia, pathogen, Providencia.